Switching power supply controlling circuit and controlling method thereof

ABSTRACT

This invention provides a switching power supply controlling circuit, the switching power supply comprises an upper transistor and a lower transistor, the switching power supply controlling circuit comprises a boost circuit, an input terminal of the boost circuit is connected to an input terminal of the switching power supply, the boost circuit output a first voltage to control a working state of the boost circuit, driving the upper transistor to be in an on state. The switching power supply controlling circuit adopts a boost circuit to provide a driving power for the upper transistor, and there is no need to set a bootstrap pin or a bootstrap capacitor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This Non-provisional application claims priority under 35 U.S.C. §119(a) on Chinese Patent Application No(s). 201910777850.5 filed on Aug.22, 2019, the entire contents of which are hereby incorporated byreference.

BACKGROUND OF THE INVENTION Field of the Invention

This invention relates to a technical field of power electronics, andmore particularly, to a switching power supply controlling circuit and acontrolling method thereof.

Description of the Related Art

In the prior art, FIG. 1 shows a schematic diagram of a control circuitof a buck converter, and FIG. 2 shows a schematic diagram of a controlcircuit of a step-up circuit. In order to drive the upper transistor Q1of the boost converter or the buck converter, a bootstrap capacitor Cbsneeds to be set. A first terminal of the bootstrap capacitor Cbs isconnected to a common terminal SW of the upper transistor Q1 and thelower transistor Q2, and a second terminal of the bootstrap capacitorCbs is connected to an input terminal of the boost converter or the buckconverter through a diode. In the prior art, the bootstrap capacitor Cbsand the bootstrap pin BST must be set, and the bootstrap capacitor Cbsis large, which is not easy to be integrated in a chip, increasing thecircuit area and design cost.

BRIEF SUMMARY OF THE INVENTION

The object of the invention is to provide a control circuit and acontrol method of a small area switching power supply, which are used tosolve the problem of setting a bootstrap capacitor in the prior art.

In order to achieve above-mentioned objectives, this invention providesa switching power supply controlling circuit, the switching power supplyincludes an upper transistor and a lower transistor, the switching powersupply controlling circuit includes a boost circuit, an input terminalof the boost circuit is connected to an input terminal of the switchingpower supply, the boost circuit output a first voltage to control aworking state of the boost circuit, driving the upper transistor to bein an on state.

Optionally, the switching power supply controlling circuit further mayinclude an auxiliary circuit, the auxiliary circuit may receive thefirst voltage, and an output terminal of the auxiliary circuit may beconnected to a control terminal of the upper transistor to control theupper transistor to be in an off state.

Optionally, the boost circuit may receive a first control signal, theauxiliary circuit may receive a second control signal, the first controlsignal may be provided to control the boost circuit to work, and thesecond control signal may be provided to control the auxiliary circuitto off the upper transistor.

Optionally, the boost circuit may include a first inductor, a switchtransistor, a rectification transistor and a first capacitor; a firstterminal of the first inductor may be connected to an input terminal ofthe switching power supply, a second terminal of the first inductor maybe connected to a first terminal of the switch transistor, a secondterminal of the switch transistor may be connected to ground, a controlterminal of the switch transistor may receive the first control signal;a first terminal of the rectification transistor may be connected to acommon terminal of the first inductor and the switch transistor, asecond terminal of the rectification transistor may be connected to afirst terminal of the first capacitor, a second terminal of the firstcapacitor may be connected to a second terminal of the upper transistor,a first terminal of the upper transistor may be an input terminal or anoutput terminal of the switching power supply, and a voltage of thefirst capacitor may be the first voltage.

Optionally, the boost circuit further may include a clamping circuit,and the clamping circuit and the first capacitor may be connected inparallel.

Optionally, the auxiliary circuit may include a second switchtransistor, a first terminal of the second switch transistor may beconnected to a control terminal of the upper transistor, a secondterminal of the second switch transistor may be connected to a firstterminal of the first capacitor, and a control terminal of the secondswitch transistor may be connected to an input terminal the switchingpower supply.

Optionally, the auxiliary circuit further may include a third switchtransistor, a first terminal of the third switch transistor may beconnected to a control terminal of the upper transistor, a secondterminal of the third switch transistor may be connected to ground, anda control terminal of the third switch transistor may receive the secondcontrol signal.

Optionally, the switching power supply may be a boost converter or abuck converter.

Optionally, the switching power supply controlling circuit may beintegrated into a chip, and a lead inductor of the chip may be providedas the first inductor.

This invention also provides a switching power supply controllingmethod, the switching power supply includes an upper transistor and alower transistor, the controlling method includes: connecting an inputterminal of the switching power supply with an input terminal of a boostcircuit, outputting an first voltage from the boost circuit to control aworking state of the boost circuit, driving the upper transistor to bein an on state; and receiving the first voltage by an auxiliary circuit,connecting a control terminal of the upper transistor with an outputterminal of the auxiliary circuit to control the upper transistor to bein an off state.

Compared with the prior art, the invention has the following advantages:connecting an input terminal of the switching power supply with an inputterminal of a boost circuit, outputting an first voltage from the boostcircuit to control a working state of the boost circuit, driving theupper transistor to be in an on state; and receiving the first voltageby an auxiliary circuit, connecting a control terminal of the uppertransistor with an output terminal of the auxiliary circuit to controlthe upper transistor to be in an off state. The switching power supplycontrolling circuit adopts a boost circuit to provide a driving powerfor the upper transistor, and there is no need to set a bootstrap pin ora bootstrap capacitor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a control circuit of a buck converterin the prior art;

FIG. 2 is a schematic diagram of a control circuit of a boost converterin the prior art;

FIG. 3 is a control block diagram of a buck converter of to thisinvention;

FIG. 4 is a control block diagram of a boost converter of to thisinvention;

FIG. 5 is a schematic diagram of a control circuit of the buck converterto this invention;

FIG. 6 is a schematic diagram of a control circuit of the boostconverter to this invention; and

FIG. 7 is an operation waveform diagram to this invention.

DETAILED DESCRIPTION OF THE INVENTION

The preferable embodiments of this invention are described in detailbelow in combination with the accompanying drawings. However, thisinvention is not limited to these embodiments. This invention covers anyalternatives, modifications, equivalent methods, and equivalentsolutions within the spirit and scope of this invention.

In order to make the public have a thorough understanding on thisinvention, specific details are described in the following preferableembodiments of this invention, while those skilled in the art will fullyunderstand this invention without descriptions of these details.

This invention is described more specifically in a way of takingexamples with reference to the accompanying drawings in the followingparagraphs. It should be noted that all the accompanying drawings are ina simplified form and not in accurate proportions, which are merely forconveniently and clearly illustrating embodiments of this invention.

FIG. 3 shows a control block diagram of a buck converter of to thisinvention. The buck converter includes an upper transistor Q1, a lowertransistor Q2, a inductor L1, and a capacitor C2. The upper transistorQ1 is a main switch transistor, and the lower transistor Q2 is arectification transistor. A first terminal of the upper transistor Q1receive an input voltage VIN, a second terminal of the upper transistoris connected to a first terminal of the lower transistor Q2, and asecond terminal of the lower transistor Q2 is connected to ground. Acommon terminal SW of the upper transistor Q1 and the lower transistorQ2 is connected to a first terminal of the inductor L1, a secondterminal of the inductor L1 is connected to a first terminal of thecapacitor C1, and a second terminal of the capacitor C2 is connected toground. A control circuit of the buck converter includes a boost circuitto drive the upper transistor Q1 using a parasitic inductance of a lineand a bond-wire inductance of a pin generated in a integration of thecontrol circuit as an energy storage inductance of the boost circuit,that is, the bond-wire inductance in the figure. The control circuit ofthe buck converter further includes a pulse generation circuit, and thepulse generation circuit output a plurality of pulse signals, to drivethe boost circuit of the control circuit and to control a working stateof the lower transistor Q2 respectively.

FIG. 4 shows a control block diagram of a boost converter of to thisinvention. The boost converter includes an upper transistor Q1, a lowertransistor Q2, a inductor L1, and a capacitor C2. The upper transistorQ1 is a synchronous rectification switch transistor, and the lowertransistor Q2 a main switch transistor. A first terminal of the uppertransistor Q1 is connected to a first terminal of the capacitor C2 as anoutput terminal, a second terminal of the capacitor C2 is connected toground, a second terminal of the upper transistor Q1 is connected to afirst terminal of the lower transistor Q2, and a second terminal of thelower transistor Q2 is connected to ground. A common terminal SW of theupper transistor Q1 and the lower transistor Q2 is connected to a firstterminal of the inductor L1, and a second terminal of the inductor L1 isconnected to and receive an input voltage VIN. The controlling circuitof the boost converter further includes a boost circuit to drive theupper transistor Q1 using a parasitic inductance of a line and abond-wire inductance of a pin generated in a integration of the controlcircuit as an energy storage inductance of the boost circuit, that is,the bond-wire inductance in the figure. The control circuit of the buckconverter further includes a pulse generation circuit, and the pulsegeneration circuit output a plurality of pulse signals, to drive theboost circuit of the control circuit and to control a working state ofthe lower transistor Q2 respectively.

FIG. 5 shows a schematic diagram of a control circuit of the buckconverter to this invention. The control circuit includes a boostcircuit, an auxiliary circuit, and a pulse generation circuit. The boostcircuit includes a first switch transistor Q3, a first inductor L2, afirst capacitor C3, a diode D1, and a first stabilivolt D2. Theauxiliary circuit includes a second switch transistor Q4 and a thirdswitch transistor Q5. The diode D1 is used as a rectification transistorof the boost circuit, and the first stabilivolt D2 is used as a clampingcircuit to clamp an output voltage of the boost circuit. A firstterminal of the first inductor L2 is connected to an input terminal ofthe buck converter, a second terminal of the first inductor L2 isconnected to a first terminal of the first switch transistor Q3, and asecond terminal of the first switch transistor Q3 is connected toground. A control terminal of the first switch transistor Q3 receive thefirst control signal pulse1. An anode of the diode D1 is connected to acommon terminal of the first inductor L2 and the first switch transistorQ3, a cathode of the diode D1 is connected to a first terminal of thefirst capacitor C3, and a second terminal of the first capacitor C3 isconnected to a second terminal of the upper transistor Q1. A firstterminal the upper transistor Q1 is an input terminal of the buckconverter; the first stabilivolt D2 and the first capacitor C3 areconnected in parallel, and a first terminal of the second switchtransistor Q4 is connected to a control terminal of the upper transistorQ1. A second terminal of the second switch transistor Q4 is connected toa common terminal of the diode D1 and the first capacitor C3, and acontrol terminal of the second switch transistor Q4 is connected to theinput terminal of the buck converter in this embodiment of thisinvention. A first terminal of the third switch transistor Q5 isconnected to the control terminal of the upper transistor Q1, a secondterminal of the third switch transistor Q5 is connected to ground, acontrol terminal of the third switch transistor Q5 receive a secondcontrol signal pulse2. The pulse generation circuit generate the firstcontrol signal pulse1, the second control signal pulse2, and a controlsignal to drive a switch state of the lower transistor. A workingprocess of the control circuit of the buck converter is as follows:

L1 inductor in energy storage phase: the first control signal is appliedfrom the control terminal of the first switch transistor Q3. When thefirst switch transistor Q3 is in an on state, the inductor L2 storesenergy, and an on-state resistance of the first switch transistor Q3plays a role of limiting current. When the first switch transistor Q3 isin an off state, a current from the first inductor L2 charges thecapacitance C3 through the diode D1, which raise a negative voltage ofthe first stabilivolt D2. When a voltage of the capacitor is higher thana first threshold value Vsw+VTH (VTH is a gate threshold voltage of Q4),the second switch transistor Q4 is in an on state, and a capacitancevoltage of the first capacitor C3 is applied to a gate-source of theupper transistor Q1, and the upper transistor Q1 is in an on state.

L1 inductor in energy releasing phase: the second control signal isapplied from the control terminal of the third switch transistor Q5.When the third switch transistor Q5 is in an on state, discharge a gateof the upper transistor Q1 to make the upper transistor Q1 in an offstate, and then the pulse generation circuit output a pulse signal todrive Q2 to be in an on state to enable freewheeling.

FIG. 6 shows a schematic diagram of a control circuit of the boostconverter to this invention. The difference between the boost converterin FIG. 6 and the step-down control circuit in FIG. 5 is as follows: thecontrol terminal of the second switch transistor Q4 is connected to anoutput terminal of a boost circuit in this invention. A working processis as follows:

L1 inductor in energy storage phase: the second control signal isapplied from the control terminal of the third switch transistor Q5, thethird switch transistor Q5 s in an on state and discharges a gate of thelower transistor Q2 to make the lower transistor Q2 in an off state, andthen the pulse generation circuit output a pulse signal to drive theupper transistor Q1 to be in an on state, and the inductor L1 storageenergy.

L1 inductor in energy releasing phase: the upper transistor Q1 is in anoff state, and a current of the inductor L1 freewheels through the diodeof the lower transistor Q2. The first control signal is applied from thecontrol terminal of the first switch transistor Q3. When the firstswitch transistor Q3 is in an on state, the first inductor L2 storageenergy, and an on-state resistance (RDSON) of the first switchtransistor Q3 plays a role of limiting current. When the first switchtransistor Q3 is in an off state, a current from the first inductor L2charges the first capacitor C3 through the diode D1, which raise anegative voltage of the first stabilivolt D2. When a voltage of thefirst capacitor is higher than a first threshold value Vsw+VTH (VTH is agate threshold voltage of Q4), the second switch transistor Q4 is in anon state, and a capacitance voltage of the first capacitor C3 is appliedto a gate-source of the lower transistor Q2, and the lower transistor Q2is in an on state to perform synchronous rectification.

FIG. 7 shows an operation waveform diagram to this invention. The Q1-GSwaveform in the figure characterizes an on/off state of the uppertransistor Q1, the Q2-GS waveform characterizes an on/off state of thelower transistor Q2, and the Q3-GS waveform characterizes an on/offstate of the first switch transistor Q3. The Q5-GS waveformcharacterizes an on/off state of the third switch transistor Q5. Whenthe first switch transistor Q3 is turned on briefly, the lowertransistor Q2 is controlled to be in an off state, and the uppertransistor Q1 to be in an on state. When the third switch transistor Q5is in an on state briefly, the upper transistor Q1 is controlled to bein an on state and the lower transistor Q2 to be in an off state.

Although embodiments are separately described and illustrated in theforegoing, while with respect to partial common technology, from theview of those skilled in the art, it is possible to replace andintegrate embodiments. Another recorded embodiment can be used forreference referring to the content that is not explicitly described inone embodiment.

The above-mentioned implement ways are not intended to limit theprotection scope of this technical solution. Any modifications,equivalent substitutions, and improvements within the spirit andprinciple of the above-mentioned implement ways should be included inthe protection scope of this technical solution.

What is claimed is:
 1. A switching power supply controlling circuit,wherein a switching power supply comprises an upper transistor and alower transistor, the switching power supply controlling circuitcomprises a boost circuit, an input terminal of the boost circuit isconnected to an input terminal of the switching power supply, the boostcircuit output a first voltage to drive the upper transistor to be in anon state; wherein the switching power supply controlling circuit furthercomprises an auxiliary circuit the auxiliary circuit receives the firstvoltage, and an output terminal of the auxiliary circuit is connected toa control terminal of the upper transistor to control the uppertransistor to be in an off stat.
 2. The switching power supplycontrolling circuit according to claim 1, wherein the boost circuitreceives a first control signal, the auxiliary circuit receives a secondcontrol signal, the first control signal is provided to control theboost circuit to work, and the second control signal is provided tocontrol the auxiliary circuit to off the upper transistor.
 3. Theswitching power supply controlling circuit according to claim 2, whereinthe boost circuit comprises a first inductor, a switch transistor, arectification transistor and a first capacitor; wherein a first terminalof the first inductor is connected to an input terminal of the switchingpower supply, a second terminal of the first inductor is connected to afirst terminal of the switch transistor, a second terminal of the switchtransistor is connected to ground, a control terminal of the switchtransistor receives the first control signal; a first terminal of therectification transistor is connected to a common terminal of the firstinductor and the switch transistor, a second terminal of therectification transistor is connected to a first terminal of the firstcapacitor, a second terminal of the first capacitor is connected to asecond terminal of the upper transistor, a first terminal of the uppertransistor is an input terminal or an output terminal of the switchingpower supply, and a voltage of the first capacitor is the first voltage.4. The switching power supply controlling circuit according to claim 3,wherein the boost circuit further comprises a clamping circuit, and theclamping circuit and the first capacitor are connected in parallel. 5.The switching power supply controlling circuit according to claim 4,wherein the switching power supply is a boost converter or a buckconverter.
 6. The switching power supply controlling circuit accordingto claim 3, wherein the switching power supply is a boost converter or abuck converter.
 7. The switching power supply controlling circuitaccording to claim 3, wherein the switching power supply controllingcircuit are integrated into a chip, and a lead inductor of the chip isprovided as the first inductor.
 8. The switching power supplycontrolling circuit according to claim 2, wherein the auxiliary circuitcomprises a second switch transistor, a first terminal of the secondswitch transistor is connected to a control terminal of the uppertransistor, a second terminal of the second switch transistor isconnected to a first terminal of the first capacitor, and a controlterminal of the second switch transistor is connected to an inputterminal the switching power supply.
 9. The switching power supplycontrolling circuit according to claim 8, wherein the auxiliary circuitfurther comprises a third switch transistor, a first terminal of thethird switch transistor is connected to a control terminal of the uppertransistor, a second terminal of the third switch transistor isconnected to ground, and a control terminal of the third switchtransistor receives the second control signal.
 10. The switching powersupply controlling circuit according to claim 9, wherein the switchingpower supply is a boost converter or a buck converter.
 11. The switchingpower supply controlling circuit according to claim 8, wherein theswitching power supply is a boost converter or a buck converter.
 12. Theswitching power supply controlling circuit according to claim 2, whereinthe switching power supply is a boost converter or a buck converter. 13.The switching power supply controlling circuit according to claim 1,wherein the switching power supply is a boost converter or a buckconverter.
 14. A switching power supply controlling method, wherein theswitching power supply comprises an upper transistor and a lowertransistor, wherein the controlling method comprises: connecting aninput terminal of the switching power supply with an input terminal of aboost circuit, outputting an first voltage from the boost circuit tocontrol a working state of the boost circuit, driving the uppertransistor to be in an on state; and receiving the first voltage by anauxiliary circuit, connecting a control terminal of the upper transistorwith an output terminal of the auxiliary circuit to control the uppertransistor to be in an off state.